The prior application (U.S. Ser. No. 09/667,640) as shown in FIG. 1 disclosed a door lock set including: a housing 1; an upper cam 2 operatively retracting an upper latch 3; a first linking rod 4 having an upper pin 41 slidably engaging in a left arcuate slot portion 22 of the arcuate slot 21 formed in the upper cam and a lower pin 42 slidably engaging with a slot 621 in a left lug 62 of a lower cam 6 having a spindle 61 rotatably mounted in a holding plate 60 as cushioned by a coiled spring 64; a second linking rod 5 having an upper pin 51 slidably engaging in a right arcuate slot portion 23 of the arcuate slot 21 and a lower pin 52 slidably engaging with a slot 631 in a right lug 63 of the lower cam 6; with the lower cam 6 operatively retracting a lower latch 7.
The prior application is especially suitable for use in a lever handle lock set having a small rotating angle when rotating either spindle (20 or 61) of the cam (2 or 6), not suitable for a door-knob type lock set, which will be explained hereinafter.
As shown in FIG. 2, a conventional door-knob type lock set includes: a door knob K which is rotated either clockwise R1 or counterclockwise R2 to allow either shoulder projection S1 or S2 formed on the knob spindle S to rearwardly push either lug L1 or L2 formed on a rear end portion of the latch bolt B for retracting the latch bolt B for opening a door. The door knob K (namely the spindle S) should be rotated in a wide or large angle in order to obtain an enough stroke for retracting the latch bolt B for opening the door.
Inferentially, if the prior application (U.S. Ser. No. 09/667,640 as illustrated in FIG. 1) is adapted for use as a door-knob type lock set as shown in FIG. 2, it will be described as follows:
When the knob K is rotated in an angle larger than a biasing angle A1 as shown in dotted line of FIG. 1, the linking rod 4 will be obstructed by the spindle 20 of the upper cam 2. Since a door knob K will require a larger or wider rotating angle A2 such as shown in phantom line of FIG. 1, the prior application is therefore not suitable for use in a door-knob type lock set because the two linking rods 4, 5 will be easily obstructed or retarded by the spindle 20 of the cam 2.
Therefore, the present inventor has found this drawback of the prior application and invented the present continuation-in-part for a larger rotating angle for a door-knob type lock set.
The object of the present invention is to provide a door lock set including: a housing fixed on a door; an upper cam rotatably mounted on an upper portion of the housing and operatively retracting an upper latch by a thumbturn knob; a lower cam rotatably mounted on a lower portion of the housing and operatively retracting a lower latch by rotating a door knob secured to a spindle of the lower cam; a linking device having an upper linking plate pivotally secured to the upper cam, a first linking rod and a second linking rod respectively upwardly pivotally secured to the upper linking plate and respectively downwardly pivotally secured to the lower cam, whereby the spindle can be rotated in a large angle for rotating the lower cam for retracting the lower latch and for synchronously biasing the upper cam for retracting the upper latch for opening the door, thereby being suitable for a door-knob type lock set; and the linking device may be optionally disposed on a right side portion of the upper cam for retracting the latch as provided on a right side of the door; or the linking device may be optionally disposed on a left side portion of the upper cam for retracting the latch as provided on a left side of the door.